Proceedings of the Zoological Institute RAS
Vol. 313, No. 2, 2009, рр. 153–167
УДК 57.072:551.762.2
STEGOSAUR REMAINS FROM THE MIDDLE JURASSIC OF WEST SIBERIA
A.O. Averianov1* and S.A. Krasnolutskii2
1
Zoological Institute of the Russian Academy of Sciences, Universitetskaya Emb. 1, 199034 Saint Petersburg, Russia;
e-mail: [email protected]
2
Sharypovo Regional Museum, 2nd microrayon 10, Sharypovo, 662311 Krasnoyarsk Territory, Russia;
e-mail: [email protected]
ABSTRACT
The Middle Jurassic (Bathonian) Itat Formation at Berezovsk Quarry, Krasnoyarsk Territory (West Siberia,
Russia) has produced abundant remains of stegosaurs. Numerous isolated teeth are found at various microvertebrate
sites, and associated skeletal remains, mostly vertebrae, ribs, and ilio-sacral block fragments were excavated at the
Stegosaur Quarry. These remains likely belong to one taxon which is characterized by numerous secondary ridges on
one crown side in cheek dentition, six vertebrae in the synsacrum, four sacral and one dorsosacral ribs, lack of dorsal
process on the transverse process in anterior caudals, moderately expanded tops of the neural spines in anterior
caudals, and large triangular transversely thin dorsal dermal plates. The combination of these and other features is
not characteristic for any other known stegosaur taxon and the Berezovsk stegosaur likely represents a new taxon.
Among known stegosaurs it is most similar with Stegosaurus from the Late Jurassic and Early Cretaceous of North
America and Asia by having numerous secondary ridges on teeth, a right angle between the supraacetabular flange
and the anterior iliac process of ilium and in the structure of the dorsal dermal plates. It differs from Stegosaurus by
plesiomorphically unexpanded tops of the neural spines and lack of dorsal process on the transverse processes in the
anterior caudal vertebrae. The Berezovsk stegosaur is among the oldest stegosaurs in the fossil record.
Key words: Dinosauria, Middle Jurassic, Russia, Stegosauria, West Siberia
Submitted March 10, 2009; accepted April 27, 2009.
ОСТАТКИ СТЕГОЗАВРОВ ИЗ СРЕДНЕЙ ЮРЫ ЗАПАДНОЙ СИБИРИ
А.О. Аверьянов1* и С.А. Краснолуцкий2
1
Зоологический институт Российской академии наук, Университетская наб. 1, 199034 Санкт-Петербург, Россия;
e-mail: [email protected]
2
Шарыповский краеведческий музей, 2-й микрорайон 10, Шарыпово, 662311 Красноярский край, Россия;
e-mail: [email protected]
РЕЗЮМЕ
Многочисленные остатки стегозавров обнаружены в отложениях среднеюрской (бат) итатской свиты,
вскрытой в Березовском карьере Красноярского Края (Западная Сибирь, Россия). Многочисленные изолированные зубы происходят из различных местонахождений микропозвоночных в карьере. Ассоциированные
скелетные остатки (в основном позвонки, ребра и фрагменты подвздошно-крестцового блока) найдены в
“стегозавровом раскопе”. Эти остатки, вероятно, принадлежат особям одного таксона, который характеризу-
* Corresponding author / Автор-корреспондент.
154
A.O. Averianov and S.A. Krasnolutskii
ется многочисленными вторичными гребнями на одной стороне коронки щечных зубов, шестью позвонками
в сложном крестце, четырьмя крестцовыми и одним спино-крестцовым ребрами, отсутствием дорсального
отростка на поперечных отростках передних хвостовых позвонков, умеренно расширенными вершинами
остистых отростков передних хвостовых позвонков и большими треугольными поперечно тонкими спинными костными пластинками. Комбинация этих и других признаков не характерна для какого-нибудь известного таксона стегозавров, и, поэтому, Березовский стегозавр, вероятно, принадлежит к новому таксону.
Среди известных стегозавров он наиболее сходен с Stegosaurus из поздней юры и раннего мела Северной
Америки и Азии по наличию многочисленных вторичных гребней на зубах, по прямому углу между надвертлужным флангом и передним отростком подвздошной кости и по строению спинных костных пластинок. Березовский стегозавр отличается от Stegosaurus такими примитивными чертами, как слабо поперечно
расширенные вершины остистых отростков и отсутствие дорсального отростка на поперечных отростках
передних хвостовых позвонков. Березовский стегозавр является одним из наиболее древних стегозавров известных в геологической летописи.
Kлючевые слова: Dinosauria, средняя юра, Россия, Stegosauria, Западная Сибирь
Представлена 10 марта 2009; принята 27 апреля 2009.
INTRODUCTION
The Middle Jurassic (Bathonian) beds of the
Itat Formation, revealed in the Berezovsk Quarry
on the south of Krasnoyarsk Territory, West Siberia
(Fig. 1) has produced a diverse fauna of vertebrates,
including fishes, salamanders, turtles, choristoderes,
lizards, crocodiles, pterosaurs, dinosaurs, tritylodontids, and diverse mammals (see Averianov et al.
2005 for details). This fauna is known mostly from
small sized disarticulated specimens obtained during
underwater screen-washing at various fossiliferous
strata within the Itat Formation, but in one place,
called the Stegosaur Quarry (Fig. 2), associated but
usually not articulated larger dinosaur bones were
excavated by S.A. Krasnolutskii and his assistants
during three field seasons (2005–2007). Majority of
dinosaur bones from this quarry belong to stegosaurs,
and at least two individuals are present. The bones
are irregularly scattered along the surface indicating a long period of sub-aerial exposure. The burial
was biased to mostly vertebrae, ribs, and ilio-sacral
blocks. The limb bones and dermal plates are known
from single specimens and the cranial bones are lacking altogether. The purpose of this paper is to give a
detailed morphological description to the stegosaur
remains from this quarry and the microvertebrate
sites. In the taxonomy of Stegosauria we follow the
recent revision by Maidment et al. (2008).
Tooth measurements. BCW, basal crown width;
FABL, fore-aft-basal length; TCH, tooth crown
height. All linear measurements are in mm.
Institutional abbreviations. SHRM, Sharypovo
Regional Museum, Krasnoyarsk Territory, Russia.
Fig. 1. Geographic position of Berezovsk Quarry (asterisk) on
the map of Russia (top, Krasnoyarsk Territory is in green) and in
the vicinity of Sharypovo city (bottom; the map is modified from
http://maps.google.ru/maps).
Middle Jurassic stegosaurs of West Siberia
155
Fig. 2. Stegosaur Quarry map (left) and S.A. Krasnolutskii excavating the stegosaur bones at this site (right) in the Berezovsk Quarry,
Krasnoyarsk Territory, Russia.
ZIN PH, Paleoherpetological collection, Zoological
Institute of the Russian Academy of Sciences, Saint
Petersburg, Russia.
SYSTEMATICS
Dinosauria Owen, 1842
Ornithischia Seeley, 1887
Stegosauria Marsh, 1877
Stegosauria indet.
(Figs. 3–13)
Material. ZIN PH 1–2/117 and numerous uncatalogued specimens, isolated teeth; SHRM 205/1,
posterior cervical(?); SHRM 203–204/1, anteriormost dorsals; SHRM 8/1, 9/1, 11/1, 103/1, 104/1,
122/1, 123/1, 206/1, dorsals; SHRM 3/1, 5/1, 6/1,
14/1, 15/1, 28/1, 109/1, dorsal neural arches; SHRM
12/1, dorsal neural arch with ankylosed rib; SHRM
52–56/1, 58/1, 59/1, 63/1, dorsal ribs; SHRM
17–26/1, 95–99/1, 106/1, 120/1, 121/1, caudals;
SHRM 10/1, 30/1, 200/1, 201/1, 207/1, caudal centra; SHRM 31/1, 208/1, chevrons; SHRM 210/1 and
211/1, fragmented ilio-sacral blocks; SHRM 45/1,
fragment of right anterior process of ilium; SHRM
214/1, fragment of left anterior process of ilium;
SHRM 40/1, ungual phalanx; SHRM 212/1, dorsal
dermal plate.
Description. Several dozens of isolated stegosaur
teeth were found during screen-washing at various
microvertebrate sites within the fossiliferous bed of
the Itat Formation; no teeth have been found at the
Stegosaur Quarry. The tooth morphology is typical
for stegosaurs (Fig. 3; Galton and Upchurch 2004).
The crown is covered with enamel on both sides and
slightly asymmetrical. The mesial side is more convex
and bears a greater number of denticles, five to eight
compared with three to five on the distal side. As a
result, the median cusp is slightly posterior to the
midline of the crown. The cingulum is robust and almost complete, except a short interval on one side of
the crown (labial or lingual), where it is very weak or
absent. The median cusp is closer to this crown side
than the lateral denticles, giving to the denticulated
ridge a wide V-shape in occlusal view (Fig. 3A, D).
On this crown side there is a “complex network of
secondary ridges” (Fig. 3B), which among stegosaurs
was noted previously only for Stegosaurus (Galton
and Upchurch 2004, p. 350). Also the enamel appears to be more wrinkled on this side (compare Fig.
3E, F). On the opposite side, there are fewer ridges,
156
A.O. Averianov and S.A. Krasnolutskii
Fig. 3. Isolated teeth of Stegosauria indet. from Berezovsk Quarry, Krasnoyarsk Territory, Russia (Itat Formation, Middle Jurassic) in
occlusal (A, D) and two side (other figures) views: A–C — ZIN PH 1/117; D–F — ZIN PH 2/117. Scale bar = 1 mm.
and groves between denticles are more consistent,
extending to the base of the crown (Fig. 3F). But on
other specimens (Fig. 3C) there are secondary ridges
on this side also, which are, however, confined to
the basal and central part of the crown. The root is
cylindrical, distinctly narrower than the crown and
slightly constricted below the cingulum. Some teeth
have facets on the cingulum closer to the mesial or
distal side caused apparently by occlusion with the
neighboring teeth and indicating some overlap of the
teeth in the dental series. The largest complete tooth
in the sample (ZIN PH 1/117; Fig. 3A–C) has FABL
6.7, BCW 4.5, and TCH 6.4. There are many teeth
of various sizes and with different states of dental
wear, some of which are completely eroded. Apparently, these teeth were swallowed and digested by
the animal. Some teeth were in use until the crown
was completely worn dawn and represent fungus-like
structures with a thin apically concave cap.
In all dorsal vertebrae the centra are spool-shaped
and amphiplatyan. The vertebrae SHRM 203–205/1
(Fig. 4) differ from the typical dorsals by an asymmetrical centrum in lateral view. In SHRM 204/1
the anterior intercentral articulation surface projects
ventrally below the posterior intercentral articulation
surface, while two other specimens show the reversal
condition. Specimens SHRM 204/1 and SHRM
205/1 were found in association, but SHRM 203/1
was found in a different place and may not belong to
the same individual. The parapophysis is not clearly
discernible on these specimens, but in SHRM 205/1
it is possible just below the neurocentral suture. If this
is correct, this vertebra would be a posterior cervical. Two other specimens are likely the most anterior
dorsals. The neural arch in SHRM 203/1 is high, as
in typical dorsals (the height of pedicel is ~1.4 times
the height of the centrum). In two other specimens
the neural canal is wider, and in SHRM 205/1 the
neural arch is relatively low, as in the anterior dorsal
of Huayangosaurus (Maidment et al. 2006, fig. 2A, B).
The centrum is relatively short; the centrum length
is approximately equal to centrum width in SHRM
204/1 and SHRM 205/1 and little smaller in SHRM
203/1. In SHRM 204/1 and SHRM 205/1 the intercentral articulation surfaces are more squarish
compared to the rounded surfaces in SHRM 203/1
and typical dorsals. The anterior margin of the neural
arch pedicel is with level with the centrum anterior
surface and vertical with or slightly overhanging the
latter. The posterior margin of the neural arch pedicel
is sloping towards the posterior centrum surface. The
transverse process, preserved completely on right side
of SHRM 203/1 (Fig. 4G–I), is short and oriented at
Middle Jurassic stegosaurs of West Siberia
70° to the sagittal plane. The
prezygapophyseal articulation surfaces are not fused
ventrally and are oriented at
about 45° to the sagittal plane.
The postzygapophysis, best
preserved in SHRM 203/1
(Fig. 4G, H), is anteroposteriorly elongate and projects
posteriorly beyond the posterior intercentral articulation
surface. The neural spine,
preserved in SHRM 203/1
(Fig. 4G–I), is a low plate
triangular in lateral view and
not widened dorsally.
The other dorsals (Figs.
5–6) show typical stegosaurian morphology (Galton
and Upchurch 2004). The
ventral margin of the centrum
is slightly concave or almost
straight in lateral view. The
lateral side of the centrum
is smooth, without a longitudinal ridge or depression.
The neural canal varies in
width and height (the latter
is 29–71% of the centrum
height, measured along the
anterior side). In most specimens it is relatively low and
tear-drop shaped (Fig. 5). In
some specimens with a broken
thin plate above the canal it
appears very high and narrow
Fig. 4. Posterior cervicals or anterior
dorsals of Stegosauria indet. from Berezovsk Quarry, Krasnoyarsk Territory, Russia (Itat Formation, Middle
Jurassic): A–C — SHRM 205/1, in
anterior (A), lateral (B), and posterior (C) views; D–F — SHRM 204/1,
in posterior (D), lateral (E), and
anterior (F) views; G–I — SHRM
203/1, in posterior (G), lateral (H),
and anterior (I) views.
Abbreviations: di — diapophysis;
nc — neural canal; ns — neural spine;
prz — prezygapophysis; psz — postzygapophysis. Scale bar = 5 cm.
157
158
A.O. Averianov and S.A. Krasnolutskii
Fig. 5. Dorsals of Stegosauria indet. from Berezovsk Quarry, Krasnoyarsk Territory, Russia (Itat Formation, Middle Jurassic): A–D —
SHRM 11/1, in posterior (A), ventral (B), lateral (C), and anterior (D) views; E–H — SHRM 8/1, in posterior (E), ventral (F), lateral
(G), and anterior (H) views.
Abbreviations: di — diapophysis; nc — neural canal; ns — neural spine; pa — parapophysis; prz — prezygapophysis; psz — postzygapophysis.
Scale bar = 5 cm.
Middle Jurassic stegosaurs of West Siberia
159
Fig. 6. Dorsals of Stegosauria indet. from Berezovsk Quarry, Krasnoyarsk Territory, Russia (Itat Formation, Middle Jurassic): A–C —
SHRM 123/1, in posterior (A), lateral (B), and anterior (C) views; D–F — SHRM 206/1, in posterior (D), lateral (E), and anterior (F)
views.
Abbreviations: di — diapophysis; nc — neural canal; ns — neural spine; pa — parapophysis; prz — prezygapophysis; psz — postzygapophysis.
Scale bar = 5 cm.
160
A.O. Averianov and S.A. Krasnolutskii
Fig. 7. Isolated dorsal ribs of Stegosauria indet. from Berezovsk Quarry, Krasnoyarsk Territory, Russia (Itat Formation, Middle Jurassic)
in anterior or posterior views: A — SHRM 63/1; B — SHRM 53/1; C — SHRM 54/1; D — SHRM 58/1; E — SHRM 55/1; F — SHRM
59/1; G — SHRM 52/1. Scale bar = 10 cm.
(e.g., SHRM 206/1; Fig. 6D, F), which is an artifact
of preservation (some postmortem compression of
vertebrae is also likely). The height of the pedicel
varies from 138% to 204% of the centrum height (the
mean value is 170% for nine measurements). There
is a deep pocket-like depression on the posterior side
of the neural arch pedicel above the neural canal and
between the lateral columnar buttresses supporting the postzygapophyses. The anterior side of the
pedicel above the neural canal is flat and with level
with the lateral buttresses supporting the prezygapophyses. The parapophysis is placed approximately at
the level of prezygapophyses. It has a short pedicel
in SHRM 5/1 and SHRM 8/1 (Fig. 5E, H). The
transverse processes are robust and T-shaped in cross
section, with the longitudinal supporting ridge extending ventrally between the parapophysis and the
diapophysis. As typical for stegosaurs, the transverse
processes are united between the prezygapophyses
and the neural spine. The orientation of the trans-
verse processes to the sagittal plane varies from 20°
to 65°; in the specimens with the low angle they are
almost as high as the neural spine. These specimens
possibly come from the middle of the dorsal series.
The prezygapophyses are joined ventrally and form
a U-shaped common articulation surface in most
specimens but are separated by a deep groove in
SHRM 109/1. The articulation surfaces are oriented
from 31° to 55° to the sagittal plane. Usually there
is a prominent ridge between the prezygapophyseal
articular surface and the base of the neural spine. The
anterior base of the neural spine is positioned level
with the centrum midline. The anterior and posterior
margins of the neural arch pedicel converge towards
the base of the diapophysis and zygapophyses, in
contrast with the anteriormost dorsals described
above, where the anterior margin is subvertical. The
postzygapophysis is elongated and projects posteriorly beyond the centrum. The postzygapophyseal
articular surfaces are separated by a ventral groove.
Middle Jurassic stegosaurs of West Siberia
The vertical ridge between the postzygapophyses and
the top of the neural canal is variably developed. The
neural spine is completely preserved in SHRM 8/1
and SHRM 123/1 (Figs. 5E, G, H and 6A–C). It is a
plate like-structure extending between the posterior
ends of the prezygapophyses and postzygapophyses
and slightly tapering dorsally.
There are several isolated dorsal ribs (Fig. 7).
SHRM 63/1 (Fig. 7A) with a relatively large and
massive capitular process and wider rib shaft could be
among first dorsal ribs or even the posterior cervical
ribs. The tuberculum is relatively small in all specimens. SHRM 52/1 (Fig. 7G) with the longest and
straightest shaft apparently comes from the middle
of dorsal series. The rib shaft has a T-shape in cross
section as in Stegosaurus (Gilmore 1914; Ostrom and
McIntosh 1999, pl. 20), with a perpendicular lateral
lamina in the proximal part forming a ridge in anterior view.
The sacral vertebrae are known from two fragmentary ilio-sacral blocks (SHRM 210/1 and SHRM
211/1). In SHRM 210/1 there are six coosified centra (Fig. 8), the two anterior of which are apparently
dorsosacrals. The second dorsosacral appears to share
the sacral rib with the first sacral, as in Stegosaurus
(Ostrom and McIntosh 1999, pl. 24). The first dorsosacral has a round intercentral articulation surface
which is flattened dorsally. The second dorsosacral
centrum has a prominent ventral keel. The sacral centra are longer than wide and are approximately equal
in length. The sacral neural arches are better preserved
in SHRM 211/1. The neural arch is transversely
about twice as wide in the third vertebra (sacral 1)
compared with the first vertebra (dorsosacral 1),
indicating widening of the sacral neural canal, similarly to that of Stegosaurus and Kentrosaurus. SHRM
211/1 preserves four sacral ribs and one dorsosacral
rib attached to the ilium (Fig. 12C). Stegosaurs usually have four robust sacral ribs, but in some there is
an additional slender dorsosacral rib (Gilmore 1914,
fig. 23; Galton and Upchurch 2004, p. 353). SHRM
211/1 agrees with this condition: the dorsosacral
rib is slender and anteromedially directed, while the
remaining sacral ribs are more robust and directed
more medially.
Caudal vertebrae are common at the Stegosaur
Quarry. The specimens SHRM 95–99/1 were found
in association and apparently represent a continuous caudal section of one individual. The vertebrae
SHRM 22/1 and SHRM 120/1 (Fig. 9A–C) are
161
Fig. 8. SHRM 210/1, coosified dorsosacral and sacral centra of
Stegosauria indet. from Berezovsk Quarry, Krasnoyarsk Territory,
Russia (Itat Formation, Middle Jurassic) in anterior (A), ventral
(B), and lateral (C) views.
Abbreviations: ds1–ds2 — dorsosacrals one and two; s1–s4 —
sacrals one to four; sr — sacral rib. Scale bar = 10 cm.
among the first three or four caudals. They are similar to the third caudal of Stegosaurus (Ostrom and
McIntosh 1999, pl. 25) in having a short and wide
centrum and long transverse processes directed vent-
162
A.O. Averianov and S.A. Krasnolutskii
Fig. 9. Anterior caudals of Stegosauria indet. from Berezovsk Quarry, Krasnoyarsk Territory, Russia (Itat Formation, Middle Jurassic):
A–C — SHRM 120/1, in posterior (A), lateral (B), and anterior (C) views; D–F — SHRM 121/1, in posterior (D), lateral (E), and
anterior (F) views.
Abbreviations: nc — neural canal; ns — neural spine; prz — prezygapophysis; psz — postzygapophyses; trpr — transverse process. Scale bar =
10 cm.
Middle Jurassic stegosaurs of West Siberia
Fig. 10. SHRM 31/1, chevron of Stegosauria indet. from Berezovsk
Quarry, Krasnoyarsk Territory, Russia (Itat Formation, Middle
Jurassic): dorsal (A), posterior (B), anterior (C), and lateral (D)
views. Scale bar = 5 cm.
163
rolaterally, but differ in lacking the dorsal process on
the transverse process, and the neural spine is much
less expanded distally. The neural spine gradually
widens laterally towards the distal end. It is concave
anteriorly and flat posteriorly. The zygapophyses
are widely separated and have flat articulation surfaces. In more posterior caudals (e.g., SHRM 121/1;
Fig. 9D–F) the centrum is longer and transversely
narrower, with very short transverse processes. The
neural spine bears a club-like structure on the top.
In still more posterior caudals the transverse process
disappears and the neural spine club is variably developed. There are few fragmented posterior caudals.
The centrum SHRM 201/16 is longer anteroposteriorly than transversely wide and hexagonal in cross
section, with distinct median ridges on lateral sides.
For the measurements of vertebrae see Table 1.
The chevrons are represented by two specimens,
among which SHRM 31/1 is more complete (Fig. 10).
They are similar to those of Stegosaurus (Gilmore
1914, fig. 29). The articular heads are expanded and
globular, but not united. The haemal canal is high
and oval-shaped. The shaft is long and a little curved,
with a ridge along the anterior surface and a groove
posteriorly.
Fig. 11. Fragments of ilio-sacral block of Stegosauria indet. from Berezovsk Quarry, Krasnoyarsk Territory, Russia (Itat Formation, Middle
Jurassic): A, B — SHRM 210/1, left ilium in lateral (A) and dorsal (B) views; C — SHRM 211/1, right ilium and attached sacral ribs in
ventral view.
Abbreviations: aip — anterior iliac process; dsr1 — dorsosacral rib 1; saf — supraacetabular flange; sr1–sr4 — sacral ribs one to five. Scale
bar = 10 cm.
164
A.O. Averianov and S.A. Krasnolutskii
Fig. 12. SHRM 40/1, ungual phalanx of Stegosauria indet. from
Berezovsk Quarry, Krasnoyarsk Territory, Russia (Itat Formation,
Middle Jurassic) in proximal (A), side (B), dorsal (C), and ventral
(D) views.
Abbreviation: lg — lateral groove. Scale bar = 2 cm.
The pelvic bones are present by fragmentary ilia
from two individuals (two ilio-sacral blocks SHRM
210/1 and SHRM 211/1). The acetabulum is poorly
preserved on all specimens. The most complete is the
left ilium SHRM 210/1 (Fig. 11A, B). It has a partially complete anterior iliac process. The process is
gently curved laterally and slightly ventrally, as usually for stegosaurs (Galton and Upchurch 2004, fig.
16.7; Maidment et al. 2008, fig. 2). Its anterior end,
known from two isolated specimens (SHRM 45/1 and
SHRM 214/1) is deep vertically and mediolaterally
thick along the dorsal margin. The ilium is expanded
laterally above the acetabulum as in other stegosaurs,
with a distinct supraacetabular flange. The angle
between the supraacetabular flange and the anterior
iliac process is close to 90° (a character considered
an autapomorphy for Stegosaurus by Maidment et al.
[2008]). The posterior iliac process is not complete
but seems to be prominent. The dorsal surface of the
ilium is flat.
The ungual SHRM 40/1 (Fig. 12) is the only
known identifiable limb bone from the Stegosaur
Quarry (there is also a poorly preserved shaft fragment possible from the tibia which is not catalogued
and not described here). The ungual is hoof-like, with
the proximal articular surface facing posteroventrally, convex dorsal and concave ventral surfaces. It is
asymmetrical in dorsal/ventral view suggesting that
it comes from a side digit. Along one side there is a
deep cleft for the claw sheath (lateral groove on Fig.
12B), not present on the opposite side. The distal end
Fig. 13. SHRM 212/1, dorsal dermal plate of Stegosauria indet.
from Berezovsk Quarry, Krasnoyarsk Territory, Russia (Itat Formation, Middle Jurassic) in lateral (A), posterior (B), and ventral
(C) views. Scale bar = 10 cm.
is blunt and truncated. There are several relatively
large vascular foramina concentrated at the distal
part of the ungual.
SHRM 212/1 is a poorly preserved but relatively
complete dorsal dermal plate (Fig. 13). It is a very
thin transversely triangular asymmetrical plate with
a somewhat thicker ventral base. The ventral surface
is slightly concave. There are some vascular grooves
on the lateral sides but they are obscured by numerous cracks.
DISCUSSION
The comparison of the stegosaur remains from
Berezovsk Quarry with other stegosaurs is limited
by fragmentary nature of these remains. Based on the
recent phylogenetic work by Maidment et al. (2008)
these remains show the following phylogenetically
informative characters: 1) horizontal lateral enlargement of the ilium present (unambiguous synapomorphy for Thyreophora); 2) dermal armor, including
scutes, spines and/or plates present (unambiguous
synapomorphy for Thyreophora); 3) transverse processes of dorsal vertebrae project at a high angle to the
horizontal (synapomorphy for Thyreophoroidea +
Emasaurus or for Thyreophoroidea depending on op-
165
Middle Jurassic stegosaurs of West Siberia
Table 1. Measurements (in mm) of vertebrae of Stegosauria indet. from Berezovsk Quarry, Krasnoyarsk Territory, Russia; upper part
of the Itat Formation, Middle Jurassic (Bathonian). Abbreviations: ACH, anterior height of centrum; ACW, anterior width of centrum;
ANW, anterior width of neural arch (between lateral margins of prezygapophyses); CL, centrum length (ventral); NAL, neural arch length
(between anterior and posterior margins of ventral floor of neural canal); NSL, neural spine length (maximum); PCH, posterior height of
centrum; PCW, posterior width of centrum; PNW, posterior width of neural arch (between lateral margins of postzygapophyses).
SHRM
number
ACH
ACW
205
40.5
50.5
—
46.3
—
204
50.8
—
—
41.8
203
58.0
—
—
46.4
ANW
CL
NAL
NSL
PCH
PCW
PNW
—
42.0
55.5
—
—
—
45.0
—
—
—
—
57.0
59.5
—
35.4
83.5
97.7
49.8
posterior cervical or anterior dorsal vertebrae
dorsal vertebrae
18
84.3
93.0
67.1
36.8
—
26
84.8
92.0
—
42.1
—
—
81.2
89.4
—
24
81.5
78.1
—
44.0
44.9
29.8
81.3
75.5
46.5
22
83.4
95.4
75.4
45.9
—
33.5
84.4
101.6
60.5
19
84.0
92.4
82.3
47.4
45.4
33.1
82.4
84.5
50.1
21
81.0
80.5
—
47.5
—
33.0
79.8
75.3
—
23
78.1
72.9
—
47.8
—
—
77.4
73.8
—
20
61.4
57.4
—
50.2
—
35.0
63.2
56.5
—
17
66.6
61.1
39.0
52.2
45.5
35.6
66.1
59.9
35.3
123
63.3
53.2
72.4
60.8
62.0
59.5
53.2
50.6
67.1
9
—
—
—
67.0
—
—
52.3
62.3
51.3
7
65.9
66.9
60.2
67.9
108.6
55.2
66.3
68.2
51.3
103
72.8
70.9
72.0
68.9
65.0
—
69.9
68.9
—
206
69.5
55.8
76.8
71.6
67.4
—
72.6
66.3
—
8
65.2
66.3
58.0
73.1
114.5
—
64.3
68.4
—
122
67.3
63.6
—
74.8
—
—
65.4
65.4
—
11
52.5
56.6
48.3
75.4
—
—
—
—
—
104
65.7
64.4
—
77.3
79.9
—
64.5
61.9
56.7
5
—
—
51.2
—
116.7
53.4
—
—
39.9
16
—
—
—
—
—
—
82.4
—
57.3
12
—
—
—
—
—
—
—
—
51.0
109
—
—
69.6
—
—
—
—
—
60.8
95
74.1
68.4
40.3
54.7
51.2
30.5
74.4
68.7
—
96
72.4
73.4
—
55.3
—
33.3
76.3
70.4
39.1
97
69.7
67.3
47.3
55.2
45.2
30.0
72.2
69.3
35.0
caudal vertebrae
98
—
—
—
51.5
—
30.3
65.9
55.5
—
99
76.0
74.9
—
52.6
—
—
74.5
71.3
44.4
120
76.2
100.6
79.3
49.7
32.0
30.5
86.9
100.0
60.4
22
81.3
109.2
84.2
55.6
39.1
32.5
93.5
117.6
67.6
19
86.1
100.0
88.9
57.3
52.6
34.5
92.2
94.1
55.1
106
66.9
64.2
—
59.0
47.7
34.9
71.4
59.5
29.9
17
77.0
72.5
50.0
60.6
45.7
37.3
77.0
69.0
40.4
121
83.3
91.9
—
64.0
51.1
34.8
85.6
81.4
42.2
21
96.8
99.8
—
65.8
40.5
37.5
82.3
79.6
45.3
166
timization); 4) large horizontal lateral enlargement of
the ilium present (synapomorphy for Thyreophoroidea + Emasaurus or for Thyreophoroidea depending
on optimization); 5) supraacetabular flange present
(synapomorphy for Thyreophoroidea + Emasaurus or
for Thyreophoroidea, reversed in Ankylosauria; the
same character is cited also as a DELTRAN synapomorphy for Stegosauria, convergent in Scelidosaurus);
6) anterior caudal neural spine height is greater than
the height of the centrum (unambiguous synapomorphy for Thyreophoroidea); 7) prominent, ring-like
cingulum present on maxillary teeth (unambiguous
synapomorphy for Euryopoda; this cingulum present
in all isolated teeth from Berezovsk Quarry, some of
which should be maxillary teeth); 8) prezygapophyses fused on some dorsal vertebrae (unambiguous
synapomorphy for Euryopoda); 9) manual and pedal
unguals hoof-shaped (unambiguous synapomorphy
for Euryopoda); 10) anterior iliac process projects at
an angle that diverges widely from the parasagittal
plane (unambiguous synapomorphy for Euryopoda);
11) parasagittal dorsal dermal armor is transversely
thin except at the base (ACCTRAN synapomorphy
for the clade C: Loricatosaurus, Tuojiangosaurus,
Paranthodon, and Stegosaurus).
The Berezovsk stegosaur is not referable to the
Jurassic Huayangosauridae from China (Huayangosaurus + Chungkingosaurus) because it lacks the
autapomorphic reversal for this clade: anterior iliac
process projects at an angle roughly parallel to the
parasagittal plane (Maidment et al. 2008). In Huayangosaurus the maxillary teeth lack the ring-like
cingulum (Sereno and Dong 1992; Galton and Upchurch 2004). As all isolated teeth from Berezovsk
Quarry have such a cingulum, this character will
further differentiate the Berezovsk taxon from Huayangosaurus.
The Berezovsk stegosaur lacks the dorsal process
on transverse process of anterior caudal vertebrae.
Presence of this process is an ACCTRAN synapomorphy for the clade Stegosauridae + Huayangosauridae
(actually unknown for Huayangosauridae) or a DELTRAN synapomorphy for Stegosauridae (Maidment
et al. 2008). Transverse width of tops of anterior caudal neural spines greater than anteroposterior width
is an unambiguous synapomorphy for Stegosauridae
according to Maidment et al. (2008). This character
is found in SHRM 120/1 (Fig. 9A–C), but majority
of anterior caudals from Berezovsk Quarry show the
reversal condition (e.g., Fig. 9D–F). These two char-
A.O. Averianov and S.A. Krasnolutskii
acters suggest the Berezovsk taxon is not referable to
Stegosauridae. But on the other hand, the Berezovsk
taxon possesses a synapomorphy for clade C within
the Stegosaurinae: parasagittal dorsal dermal armor
is transversely thin except at the base. Furthermore,
the materials from Berezovsk Quarry show one character considered as an unambiguous synapomorphy
for Stegosaurus: supraacetabular flange projects at 90°
from the anterior iliac process. The stegosaur teeth
from Berezovsk Quarry have a complex network of
secondary ridges, a character previously considered
unique for Stegosaurus (Galton and Upchurch 2004,
p. 350).
The stegosaur material from Berezovsk Quarry
show a unique combination of primitive and derived
character states discussed above, not found in any
other known taxon of Stegosauria. Presence of more
than one taxon in this assemblage seems unlikely. The
Bathonian Berezovsk stegosaur is among the oldest
representatives of the group. Other Middle Jurassic stegosaurs are known currently from Europe,
China, and Kyrgyzstan (Galton and Upchurch 2004;
Averianov et al. 2007; Maidment et al. 2008). The
Berezovsk stegosaur likely represents a new taxon
and we hope that discovery of more complete materials from the Berezovsk Quarry will allow its formal
description.
ACKNOWLEDGEMENTS
We thank R.V. Yushin, E.V. Yushin, and S.T. Sumin for
help with excavations and D.V. Grigoriev for assistance
with photographing. The permanent support for our work
was provided by the general director of OAO SUEKKrasnoyarsk A.V. Federov and by the chief manager of
the Berezovsk Quarry M.V. Palshin. We are grateful to the
reviewers P. Galton and S. Maidment for reading the paper
and useful suggestions.
REFERENCES
Averianov A.O., Lopatin A.V., Skutschas P.P., Martynovich N.V., Leshchinskiy S.V., Rezvyi A.S., Krasnolutskii S.A. and Fayngerts A.V. 2005. Discovery of
Middle Jurassic Mammals from Siberia. Acta Palaeontologica Polonica, 50: 789–797.
Averianov A.O., Bakirov A.A. and Martin T. 2007.
First definitive stegosaur from the Middle Jurassic of Kyrgyzstan. Paläontologische Zeitschrift, 81:
440–446.
Middle Jurassic stegosaurs of West Siberia
Galton P.M. and Upchurch P. 2004. Stegosauria. In:
D.B. Weishampel, P. Dodson and H. Osmólska (Eds.).
The Dinosauria. Second Edition. University of California Press, Berkeley, Los Angeles, London: 343–362.
Gilmore C.W. 1914. Osteology of the armored Dinosauria
in the Unites States National Museum, with special reference to the genus Stegosaurus. Bulletin of the Unites
States National Museum, 89: 1–143.
Maidment S.C.R., Norman D.B., Barrett P.M. and Upchurch P. 2008. Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia). Journal of Systematic
Palaeontology, 6: 367–407.
167
Maidment S.C.R., Wei G. and Norman D.B. 2006. Redescription of the postcranial skeleton of the Middle
Jurassic stegosaur Huayangosaurus taibaii. Journal of
Vertebrate Paleontology, 26: 944–956.
Ostrom J.H. and McIntosh J.S. 1999. Marsh’s Dinosaurs.
The Collections from Como Bluff. Yale University
Press, New Haven, London, 388 p.
Sereno P.C. and Dong Z.-M. 1992. The skull of the basal
stegosaur Huayangosaurus taibaii and a cladistic diagnosis of Stegosauria. Journal of Vertebrate Paleontology,
12: 318–343.